Dummy block detector for extrusion presses



March 28, 1961 A. J DE MATTEO 2,976,991

DUMMY BLOCK DETECTOR FOR EXTRUSION PRESSES Filed Dec. 21, 1956 CONTROL CIRCUIT FOR LOADER /z. Lil

-/0a I44 /5 INVENTOR.

i Q 4001M MAW 14 I VIII/11111112 BY M 7 Arrow/5K9 2,976,991 C Patented Mar. 28, 1961 2,976,991 DUMMY BLOCK DETECTOR FOREXTRUSION. PRESSES Adolph J. De Matteo, Berkeley Heights, N.J., assignor to Farrel-Birmingham Company, Inc., Ansonla, Conn., a corporation of Connecticut Filed Dec..2 1, 1956, Ser. No. 629,982

3 Claims. (Cl. 207-1) The present invention pertains generally to extrusion presses-and more particularly to a'protective device for detecting the presence of a pressure disc or dummy block on a billet loader and adapted to arrest the operation of the press in the absence of the block.

In the extrusion process, a'billet of solid metal is converted into a continuous length of uniform cross-section by forcing it to flow under high pressure through a die orifice which is so shaped as to impart a given profile to the end product. Extrusion presses of standard design comprise a container having a longitudinal bore for accommodating the billet, the billet being driven toward the die by a hydraulically or mechanically operated ram. Smooth working of the extrusion process requires the supply to the press ofbillets which are heated throughout to a uniformly plastic condition.

Interposed between the billet and the ram is a pressure disc which is ordinarily made from steel and acts eifectively to isolate the ram from the temperature etfects of the hot billet. Unlike the ram, the pressure disc is machined to a close tolerance with respect to the bore of the container, thereby preventing the rearward escape or back extrusion of the plastic metal when the billet is subjected to ram pressure. In the event the pressure disc is inadvertently omitted, the billet metal will force its Way backwardly through the space between the ram and the container bore as well as forwardly through the die orifice, thus fouling the ram. In such circumstances it becomes necessary to halt operation in order thoroughly to clean the ram surface of the billet metal before the extrusion process can be resumed. 1

It has heretofore been known to detect the presence of the pressure disc by means of .a'pressure-actuated microswitch. This switch is positioned to react to the weight of the disc when it is rolled onto the cradle of the loader for carrying both the billet and the disc to the bore of the container. The switch is connected in a circuit adapted to interrupt the operation of the ram in the event the disc is not in place. The drawback to this arrangement is that the microswitch operation is not reliable, for the actuator mechanism thereof may be blocked by reason of dirt and other foreign matter.

In view of the foregoing, it is the primary object of this invention to provide a protective device which indicates the presence or absence of a pressure disc and is adapted to arrest the operation of the ram until such time as the pressure disc is in place.

More particularly it is an object of theinvention to provide an electromagnetic protective system responsive to the presence of a pressure disc but insensitive to the billet on the cradle of a loading device, the system acting upon the control circuit for the ram to prevent ram move ment should the pressure disc not be in place.

Also an object of the invention is to provide a protective device of simple and inexpensive design which is efiicient and reliable in operation.

For a better understanding of the invention as well as other objects and further features thereof, reference is made 'to the following detailed description to be read in conjunction with the accompanying drawing wherein like components in the several views are identified by like reference numerals.

In the drawing:

' Fig. l is a longitudinal section taken through a typical direct extrusion press. I i

Fig. 2 is an elevational view of the press looking toward the front opening of the container.

Fig. 3 is a schematic view of the circuit of the protective device.

Referring now to the drawings, and more particularly to. Fig. 1, there is shown a typical extrusion press arrangement for the production of rods 'orsolid sections, the press comprising a container 10 constituted by a heavy steel shell fitted with alloy steel liners, and having a bore '10:: into'which is insertable a hydraulically driven extrusion ram 11. In front of the ram there is placed a pressure disc or dummy block 12.which fits the container more closely than the ram to prevent rearward extrusion of the metal. f

In operation, a solid block of preheated metalin the form of a billet 13 is inserted within the container, and the ram, actuated hydraulically, exerts the necessary pressure to force the metal toward the die, generally designated by numeral 14, and constituted by a plate insert 14a fitting into the recess on the face of a die holder 14b which in turn is supported by a bolster 14c held in the diehead 14d.

Efficient operation of the extrusion process requires the supply to the press of billets which are heated throughout to a uniform plasticity. The type of furnace used depends on the nature of the metal "forming the billet. Heated billets discharged from the-furnace are rolled down an inclined ramp 15 and are received on the cradle 16 mounted at the end of a loader arm 17 pivotally supported at the other end on a bracket 18. Also rolled down onto the cradle 16 is the dummy block 12, the block being juxtaposed with the billet in axial alignment therewith.

. As shown in Fig. 2, loader arm 17 is caused to swing upwardly about its pivot by means of a hydraulic cylinder 19 whose working piston is pivotally connected to the loader arm 17' at an intermediate point thereon. As shown in Fig. 1, when the loader is.elevated, the billet and dummy block are registered with the bore 10a inthe each side wall having a 45 degree tilt relative to the base.

Primary coil 2t) is secured to side wall 16b, while secondary coil 21 is secured to side wall 160. Both coils are disposed perpendicularly relative to the side walls, hence the longitudinal axis of coil 20 is disposed degrees relative to the axis of coil 21.

Primary coil 20 is connected to a source of alternating current, thereby establishing an electromagnetic field in the surrounding region. Cradle 16 is fabricated of nonmagnetic material, and as the coils occupy positions normal to each other, they are inductively de-coupled. Consequently no voltage is induced in secondary coil 21 in the absence of a dummy block. The presence of a billet on the cradle does not alfect the coupling or lack of it since the billet metal is of non-magnetic material.

When however thedummy block is in place on the cradle, there is provided a flux path of high permeability linking the two coils. The dummy block being of magnetic material effects an inductive coupling between the primary and secondary coils, whereby an alternating volttage is induced in the secondary coil. Indicating means, such as light .oralarm .device may be coupled to the output of the secondary coil to .call attention to the absence of 'thefdummy block.

The induced voltage is applied to an alternating voltage relay 22 or an equivalent electronic device. Energization of .relay 22 causes closure of a switch 23 connected in the power circuit for hydraulic cylinder 19 such that when switch 23 is closed, the operation of the cylinder is initiated to elevate the billet and dummy .to the extrusion .position. When the cradle reaches its elevated position in alignment with the container bore, the power circuit for the ram is automatically activated and extrusion is carried out. .But should the relay 22 not be energized by reason of the absence of a dummy, the loader will not elevate and the extrusion process will be halted until a dummy is in place.

The mechanism for operating the fiuidcylinder 19 forraising and lowering the cradle may be similar to that disclosed for the same purpose in Patent 2,429,525 to Rawlinson, issued February 21, 1947. In this prior patent, a control valve is provided for feeding .fiuid into the cylinder to raise and :lower the carrier for the billet. To adapt this arrangement to the present operation, one has merely to actuate the control valve in Rawlinson by an electrical motor or solenoid under the control of switch 23 in Fig. 3.

While there has been shown what is considered to be a preferred embodiment of the invention, it will be manifest that many changes and modifications may be made therein without departing from the essential spirit of the invention. It is intended, therefore, in the annexed claims to cover all such changes and modifications as fall Within the true scope of the invention.

What is claimed is:

1. An extrusion press comprising a container having a bore, a loader adapted to elevate a billet and a dummy block formed of magnetic material from a lower receiving position into registration with the bore to be acted upon by a ram, and protective apparatus for detecting the presence or absence of the dummy block on the loader, said apparatus including first and second electromagnetic coils mounted relative to said loader at positions thereon at which in the absence of said dummy block said coils are inductively decoupled and in the presence of said block said coils are inductively coupled through said block, means to apply an alternating voltage to said first coil,

and means coupled to said second coil and responsive to the voltage induced therein to control the operation of said loader so as to prevent elevation thereof in the absence of said dummy block.

2. An extrusion press comprising a container having a bore, a loader adapted to elevate a billet and a dummy block formed of magnetic material from a lower receiving position .into registration with the bore to be acted upon by a ram, and protective apparatus for detecting the presence or absence of the dummy block on the loader and for preventing operation of said press in the event the block is absent, said apparatus including first and second electromagnetic coils angularly mounted relative to said loader at positions thereon at which in the absence of said dummy block said coils are inductively decoupled and in the presence of said block said coils are inductively coupled through said block, means to apply an alternating voltage to said'first coil, and relay means coupled to said second coil and responsive to the voltage induced therein to control the operation of said loader so as to prevent elevation thereof in the absence of said dummy block.

3. An extrusion press comprising a container having a bore, a loader adapted to elevate a billet and a dummy block formed of magnetic material from a lower receiving position into registration with the bore to be acted upon by a ram, and protective apparatus for detecting the presence or absence of the dummy block on the loader, said loader including a cradle having a base wall and oppositely inclined side walls forming a 45 degree angle with the base wall, said apparatus including first and secondtelectromagnetic coils mounted perpendicularly on the respective side walls of said cradle whereby the axes of said coils lie in perpendicular planes such that in the absence of said dummy block said coils are inductively decoupled and in the presence of said block said coils are inductively coupled through said block, means to apply an alternating voltage to said first coil, and relay means coupled to said second coil and responsive to the voltage induced therein to control the operation of said loader so as to prevent elevation thereof in the absence of said dummy block.

References Cited in the file of this patent UNITED STATES PATENTS Germany Oct. 15, 1936 

